Oh Deer! Immune System Becomes Strong in Promiscuous Mice

Promiscuous mice can change their DNA to help boost their immune system, a new study suggests.

Researchers from the University of California, Berkeley studied two types of mice - California mouse (Peromyscus californicus) and deer mouse (Peromyscus maniculatus). These species are from the same genetic lineage and share the same habitat, but their social lives are different from each other. While the California mouse is monogamous and lives with one partner, the deer mouse is promiscuous and mates with multiple partners.

Experts tested the two species of mice at the microscopic and molecular levels. Initially they tested the bacterial communities that live in the reproductive tract of the mice. They found that the lifestyle and habitual activities of the mice had a direct impact on their bacterial communities.

They previously found that the promiscuous mice had twice the bacterial diversity in their reproductive system compared to the monogamous mice, the results of which were published in the journal Naturwissenschaften last October.

Furthermore in the study, the researchers have now found that the lifestyle of the mice can also impact the DNA of the mice that is associated with the immune system. The experts sequenced the genome of the two species of mice and compared their versions of the immunity gene known as MHC-DQa.

They found that the promiscuous mice had more diversity in their genes related to the immune system compared to the monogamous mice.

"The promiscuous mice, by virtue of their sexual system, are in contact with more individuals and are exposed to a lot more bacteria," Matthew MacManes, study author and a National Institutes of Health-sponsored post-doctoral fellow at UC Berkeley, said in a statement from the Texas Advanced Computing Center.

"They need a more robust immune system to fend off all of the bugs that they're exposed to," he said.

Researchers said that the social behavior of mice matches the behavior of humans and other species which have different mating habits. They suggested that the diversity in social behavior can cause evolutionary changes at the DNA level in a particular species.

The new findings of the study: "Is Promiscuity Associated with Enhanced Selection on MHC-DQαin Mice (genus Peromyscus)?," are published in the journal PLoS ONE.